This invention relates to a method of manufacturing a friction article wherein a fiber material having a continuous three dimensional matrix is filled with a slurry. The slurry is made up of various friction modifiers and fillers carried in a sometimes volatile solution of liquid binders. Volatiles are evaporated leaving the friction modifiers and binder in the matrix. A compressive force of about 10 Kg/cm.sup.2 can be applied to the filled fiber material to establish a greater desired density during curing of the binder to establish a second matrix which holds the friction modifiers in the first matrix.
In the past it has been common practice to manufacture friction articles by mixing together friction modifiers, reinforcing fibers, and binders. The binders when cured form a matrix for holding the reinforcing fibers and friction modifiers in a fixed relationship. The reinforcing fibers are randomly orientated to provide structural unity for the friction article. When the reinforcing fiber was asbestos this type of processing resulted in an adequate friction article. Unfortunately, asbestos has been identified as a potential material which under some circumstances may be a health hazard. As a result, other reinforcing materials such as glass fiber, steel fiber, cellulose, Kevelar, and mixtures thereof have been investigated as a replacement for asbestos. As could be expected, the processing which was developed over the years for asbestos could not be used without modification for the other reinforcing materials. For instance, both under and over blending of glass fiber results in a friction composition wherein the resulting wear and coefficient of friction are unacceptable.
In recent years much research and development has taken place in an effort to produce an open foam structure which is light weight and yet structurally uniform. U.S. Pat. Nos. 3,616,841 and 3,946,039 disclose methods of producing such a foam structure wherein the resulting matrix is substantially uniform and continuous in all three directions. These structures have a high strength to weight ratio and are used in construction of various apparatus such as aircraft structural members, heat exchanger cores, sound and shock absorbers, and filters.